Multi-layer surgical guide

ABSTRACT

A drill guide employs multiple layers of materials with different mechanical properties in order to achieve concurrent goals of rigidity, fit and retention. For example, a rigid exterior shell and a soft interior may be used together to securely and precisely fit a drill guide to a surgical site.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/167,678 filed on Jan. 29, 2014, which is a continuation-in-part ofU.S. application Ser. No. 13/951,818 filed on Jul. 26, 2013, whichclaims the benefit under 35 U.S.C. §119(e) of U.S. App. No. 61/676,734filed on Jul. 27, 2012 and U.S. App. No. 61/811,690 filed on Apr. 12,2013. The entire content of each of these applications is herebyincorporated by reference.

This application is related to U.S. application Ser. No. 12/816,710, theentire content of which is hereby incorporated by reference.

BACKGROUND

The invention relates to composite dental drill guides for use inrestorative dental surgery and similar procedures.

Dental drill guides are generally formed of rigid materials thatconstrain drill motion during a drilling procedure. However, rigidguides often do not fit properly on the teeth or fit with poor retentionbecause teeth present complex paths of insertion and the rigid materialmay not deform easily to accommodate undercuts and other variations intooth structures. There remains a need for drill guides that satisfy theconcurrent constraints of high rigidity to enforce a surgical plan, highprecision of fit to obtain proper alignment, and good retention to avoidslippage and rocking during use.

SUMMARY

A drill guide employs multiple layers of materials with differentmechanical properties in order to achieve concurrent goals of rigidity,fit and retention. For example, a rigid exterior shell and a softinterior may be used together to securely and precisely fit a drillguide to a surgical site.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following description of particularembodiments thereof, as illustrated in the accompanying drawings inwhich like reference characters refer to the same parts throughout thedifferent views. The drawings are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.

FIG. 1 shows a method for fabricating a drill guide.

FIG. 2 shows a method for fabricating a drill guide.

FIG. 3 shows a method for fabricating a drill guide.

FIG. 4 shows a method for fabricating a drill guide.

FIG. 5 shows a modified digital model, or a physical model fabricatedfrom same.

FIG. 6 shows a modified digital model, or a physical model fabricatedfrom same.

FIG. 7 shows a modified digital model, or a physical model fabricatedfrom same.

FIG. 8 illustrates steps to a method for fabricating a guide.

FIG. 9 shows a dental drill with a drill stop.

FIGS. 10A-10C illustrate steps of a technique for using a drill stop.

FIG. 11 shows a multi-layer guide.

FIG. 12 shows a method for fabricating a multi-layer drill guide.

FIG. 13 shows a physical model with a post.

FIG. 14 shows a physical model with a guide tube placed over a post.

DETAILED DESCRIPTION

Various surgical guides are described in U.S. patent application Ser.No. 12/816,710, the entire content of which is hereby incorporated byreference. Described herein are methods for fabricating such drillguides and other surgical guides using a combination of computerizedplanning and modeling that leads to the creation of a physical model. Afinal guide can then be fabricating on the physical model and a guidehole created for a drilling procedure.

As used herein, the term “axial trajectory” refers to a straight linedefined by at least two separate points that characterize an intendedpath (typically the center of the path) for a drill into a site such asa surgical site. The axial trajectory for a particular surgicaloperation may be determined, for example, using planning software or thelike prior to the surgical operation based upon three-dimensional dataacquired from the surgical site. It will be understood that while thefollowing description depicts lower-jaw drill guides, one of ordinaryskill in the relevant art may readily adapt the surgical guides andrelated procedures to an upper jaw, and all such variations are intendedto fall within the scope of this disclosure.

References to items in the singular should be understood to includeitems in the plural, and vice versa, unless explicitly stated otherwiseor clear from the text. Grammatical conjunctions are intended to expressany and all disjunctive and conjunctive combinations of conjoinedclauses, sentences, words, and the like, unless otherwise stated orclear from the context. Thus, the term “or” should generally beunderstood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting,referring instead individually to any and all values falling within therange, unless otherwise indicated herein, and each separate value withinsuch a range is incorporated into the specification as if it wereindividually recited herein. The words “about,” “approximately,” or thelike, when accompanying a numerical value, are to be construed asindicating a deviation as would be appreciated by one of ordinary skillin the art to operate satisfactorily for an intended purpose. Ranges ofvalues and/or numeric values are provided herein as examples only, anddo not constitute a limitation on the scope of the describedembodiments. The use of any and all examples, or exemplary language(“e.g.,” “such as,” or the like) provided herein, is intended merely tobetter illuminate the embodiments and does not pose a limitation on thescope of the embodiments. No language in the specification should beconstrued as indicating any unclaimed element as essential to thepractice of the embodiments.

In the following description, it is understood that terms such as“first,” “second,” “top,” “bottom,” “side,” “front,” “back,” and thelike, are words of convenience and are not to be construed as limitingterms.

FIG. 1 shows a method for fabricating a drill guide.

As shown in step 102, the method 100 may include obtaining a digital jawmodel of intraoral structures of a patient. The intraoral structures mayinclude teeth, a jawbone (with or without teeth), soft tissue, existingimplants and prosthetics, and so forth. This may, for example, includeobtaining data based upon a Cone Beam Computed Tomography scan, aComputed Tomography scan, a laser scan, an optical scan, a MagneticResonance Imaging scan, an optical scan, or any other suitable scanner.It should also be understood that, depending upon the type of scanner,the data may be captured intraorally, or the data may be captured froman impression model or the like that physically captures thethree-dimensional form of the intraoral structures. Thus for example,the digital jaw model may be obtained from a three-dimensional scan of aphysical impression of the jaw, or the digital jaw model may be obtainedfrom a three-dimensional scan of a physical model of the intraoralstructures formed from a physical impression of the jaw.

In another aspect, multiple models may be combined to obtain the digitaljaw model. For example, the method 100 may include obtaining a firstdigital model of the jaw for forming the guide and a second digitalmodel for creating the surgical plan, and combining the first digitalmodel and the second digital model to obtain the digital jaw model. Thesecond model may include three-dimensional structure of the jaw, such aswhere computed tomography is used to capture an image of bone structure.Thus for example, the second model (for creating the surgical plan) maybe based upon a Computed Tomography scan of the patient, a Cone BeamComputed Tomography scan of the patient, an x-ray scan. The first modelmay include soft tissue surrounding the jaw, such as where the scan isobtained from an optical or other external scan of the intraoralstructures (either intraorally, or from an impression model or thelike). The first model may include one or more teeth and any otherstructures present at the site of interest. Thus for example the firstmodel may be based upon an optical scan of the intraoral structures, athree-dimensional scan of a physical impression of the intraoralstructures, or a three-dimensional scan of a model formed from aphysical impression of the intraoral structures.

The multiple models (e.g., first and second models) may be combinedusing any suitable three-dimensional modeling techniques to scale andalign models from disparate sources. Suitable registration techniquesare well known in the art and are not described here in detail.

As shown in step 104, the method 100 may include creating a surgicalplan. This may include any computerized planning techniques such ascreating the surgical plan with implant planning software, or using asuitably adaptive Computer Aided Design (“CAD”) environment. In general,a surgical plan may include an axis for a dental implant that isspecified relative to the digital jaw model. The surgical plan may alsoinclude a depth for a dental implant into the jaw of the patient, whichinformation may be subsequently used to determine the depth of acorresponding cavity created in the modified digital model describedbelow.

As shown in step 106, the method 100 may include modifying the digitaljaw model to include a cavity having a predetermined orientationrelative to the axis, the cavity extending into the digital jaw model. Avariety of suitable techniques may be employed to create such a cavity,which may have a variety of shapes, sizes, and orientations. In general,the cavity provides an alignment feature that is ultimately used toalign a hole for a drill to the axis identified during the implantplanning For example, the cavity may be formed by a cylinder centered onand parallel to the axis. The cavity may be centered on the axis.

A wide variety of possible modifications are contemplated includingmodifications that create recesses into the model, as well asmodifications that create projections out from the model, e.g., toprovide for an alignment hole off of the surface where a drillingprocedure is performed. Thus in one aspect, modifying the digital jawmodel may include raising a surface of the digital jaw model above theintraoral structures in an area where the axis intersects the intraoralstructures, thereby providing a raised surface, and forming the cavityin the raised surface. This may include a cylindrical projection up fromthe surface of the intraoral structures, or any other suitably shapedand sized raised surface. The raised surface may, for example, extend toan occlusal surface of one or more adjacent teeth. The raised surfacemay also or instead extend about 6-12 mm above the intraoral structures,8-10 mm above the above the intraoral structures, about 9 mm above animplant platform, or any other suitable distance. The raised surface maybe perpendicular to the axis, and may provide a mating surfaceperpendicular to the axis for a drill stop. In one aspect, the raisedsurface may include (e.g., circumscribe or otherwise define byprojection or the like) a cylindrical body centered on the axis. Theraised surface may include a circular top or any other shape suitablefor a mating surface. The height of the raised surface from theintraoral structures may be selected for a predetermined depth of animplant hole according to the surgical plan. That is, with apredetermined drill length (e.g., from a drill stop) and a predeterminedimplant depth, a height may be calculated for the raised surface andimposed on the modified model to obtain a drill guide that limits depthto the predetermined implant depth when using a drill with thepredetermined drill length.

Thus in another aspect, the method disclosed herein may includeproviding a drill stop for a drill of predetermined dimensions that,when used in combination with the guide, creates a drill hole in theintraoral structures having the predetermined depth.

As shown in step 108, the method 100 may include fabricating a physicalmodel from the digital jaw model, the physical model including a recesscorresponding to the cavity of the digital jaw model. In this manner,the cavity used to capture alignment information for the implant plan istransferred to a physical model. This may include any suitablefabrication technique such as stereolithography, fused depositionmodeling, selective laser sintering, polyjet printing or other similarjet printing techniques, laminated object manufacturing, computerizedmilling, or any other suitable additive or subtractive fabricationtechnique.

As shown in step 110, the method 100 may include placing an insert intothe recess, the insert having an exposed top surface and an opening inthe exposed top surface. The insert may provide a variety of features tosupport fabrication of an accurate drill guide. For example, the insertmay provide a cut-resistant barrier for creation of a hole aligned tothe implant plan. The insert may also add structure to a guide formed ontop of the physical model, and/or may include a removable portion, e.g.,a metal portion, that is retained in the drill guide to provide a tubeor the like to align a drill during a drilling procedure. Several ofthese features and characteristics are now described in greater detail.

In one aspect, the exposed top surface may extend above the intraoralstructures in an area where the axis (of the implant plan) intersectsthe intraoral structures. The exposed top surface may be normal to theaxis of the surgical plan in order to provide a resting surface for adrill stop or the like used in a drilling procedure. The insert may beformed of a metal such as surgical stainless steel (particularly where aportion of the insert is retained in the guide during use), aluminum, orany other cut-resistant material such as a ceramic, a glass, a hardplastic, and a cut-resistant composite.

The insert may include a cylindrical tube having one or more features tomechanically engage the insert to the guide for use with the guideduring a surgical procedure. In this configuration, the insert mayremain in the guide (formed in step 112 below) when the guide is removedfrom the physical model, thus providing a tube of cut-resistant materialin the guide for use when drilling.

In another aspect, the insert may be a two part insert. A bottom portionmay include a post having a bottom fitted to the cavity of the physicalmodel and a top extending above the intraoral structures. A removabletop portion may include a sleeve with a cylindrical hole therethrough,wherein a bottom end of the cylindrical hole is fitted to the top of thepost and a top end of the cylindrical hole provides the opening in theexposed top surface of the insert. By fashioning the sleeve to beremovably and replaceably attached to the post, the sleeve can beremoved with the guide for use in a drilling procedure while the bottomportion remains with the physical model. Thus the method 100 may includeretaining the sleeve in the guide to guide creation of a pilot hole or ableeding point and removing the sleeve from the guide for a subsequentdrilling operation of the surgical procedure. In another aspect, themethod 100 may include removing the sleeve from the guide prior to usingthe guide for a surgical procedure. Thus the removable sleeve may beused to provide a cut-resistant barrier for creation of a hole in theguide, while being removable from the guide prior to use. The sleeve mayinclude one or more protuberances that mechanically engage the sleeve tothe guide for use with the guide during a surgical procedure.

As shown in step 112, the method 100 may include forming a guide from amaterial disposed around the physical model and the insert. This mayinclude vacuum forming a plastic sheet onto the physical model, such asa thermoplastic or a polystyrene. More generally, any thermoformingtechnique may be suitably employed, and term “vacuum forming” as usedherein is intended to include any thermoforming process or the likeunless explicitly stated to the contrary or otherwise clear from thecontext. The plastic may also or instead include cold-cured acrylic,light-cured acrylic, or any other suitable material or combination ofmaterials. Forming the guide may also or instead include molding aplastic or modeling material or the like on top of the physical modelwith any exterior surface shape suitable for intraoral use after curing.This may for example include an impression material, or any other clay,thermoplastic, or other suitable material(s).

As shown in step 114, the method 100 may include creating a hole in theguide aligned to the opening. In general, the insert provided in step110 may provide a cut resistant barrier for creation of the hole so thatthe hole is properly aligned to the implant plan. Forming the holed mayinclude creating the hole in any suitable manner. This may for exampleinclude creating the hole with a cutting instrument such as a hand-helddrill, a computer controlled drill, or a drill with an alignment fixtureor the like. The cutting instrument may more generally include anyinstrument suitable for creating a hole in the material of the guide,such as a laser, a drill, a tapered drill, a heat probe, a millingmachine, a computer numerically controlled milling machine, acomputer-controlled drill, a hot knife, and so forth.

As shown in step 116, the method may include removing the guide from thephysical model.

As shown in step 118, the method may include trimming the guide toremove the guide from the physical model. This may include trimming theguide for use with the jaw of the patient, such as by removing excessmaterial that would not fit within the intraoral site, or that mightcause patient discomfort or otherwise interfere with proper use of theguide. More generally, this may include any suitable finishing stepssuch as trimming sharp and/or angular edges, sanding or otherwisesmoothing corners, cleaning, and so forth.

In another aspect the method may include creating depth stop for theguide. Based upon the computerized implant plan and digital jaw model,the height of the guide can be determined. As such, a depth guide can bereadily designed for a drill having a predetermined length such that thedrill will go a predetermined depth into the intraoral structures whenused with the guide and with the depth stop. Accordingly, the method mayinclude providing a depth stop for the guide, the depth stop including:a cylindrical body having an outside diameter matched to the hole in theguide and an inside diameter providing an interference fit to apredetermined drill; and a flange having an outside diameter greaterthan the hole in the guide, the flange stopping an insertion of thepredetermined drill into the hole at a predetermined depth.

FIG. 2 shows a method for fabricating a drill guide. In general, thetechniques described above cover creation of a cavity in the digital jawmodel to receive an insert. While the cavity described above may beplaced within an elevated surface that is also added to the model, thisdoes not cover the general case where the modifications to the digitalmodel do not include any cavity whatsoever. Instead, the modificationmay include the creation of a post such as a cylinder or the likeextending above the surface of the intraoral structure. Instead of aninsert, a metal sleeve may then be placed around the post and used as acut-resistant barrier during creation of a hole. Such embodiments aregenerally described in the method 200 below, which method includes stepssimilar to those described above except as specifically noted.

As shown in step 202, the method 200 may include obtaining a digital jawmodel of intraoral structures of a patient.

As shown in step 204, the method 200 may include creating a surgicalplan for a dental implant in the intraoral structures, the surgical planincluding an axis for the dental implant, wherein the axis is specifiedrelative to the digital jaw model.

As shown in step 206, the method 200 may include modifying the digitaljaw model to include a rod extending from the intraoral structuresformed by a cylinder centered on and parallel to the axis.

As shown in step 208, the method 200 may include fabricating a physicalmodel from the digital jaw model, the physical model including a postcorresponding to the rod of the digital jaw model.

As shown in step 210, the method 200 may include placing a sleeve aroundthe post, the sleeve having an open, cylindrical interior shaped andsized to be removably and replaceably fitted to the post, and the sleevehaving an exposed top surface extending above the post and an opening inthe top surface formed by a top end of the open, cylindrical interior.It will be appreciated that while a cylindrical post and sleeve areconvenient, simple geometries suitable for use with conventional drills,other geometries may readily be adapted to use with the systemsdescribed herein. For example, a post with a square or triangular crosssection and appropriate dimensions can uniquely position a cylindricalsleeve placed thereupon.

As shown in step 212, the method 200 may include forming a guide from amaterial disposed around the physical model and the sleeve.

As shown in step 214, the method 200 may include creating a hole in theguide aligned to the opening.

As shown in step 216, the method 200 may include removing the guide fromthe physical model, which may include removing the guide and the sleevefrom the physical model, or removing the guide without the sleeve fromthe physical model.

As shown in step 218, the method 200 may include trimming the guide toremove the guide from the physical model. This may include trimming theguide for use with the jaw of the patient.

FIG. 3 shows a method for fabricating a drill guide. In the followingmethod 300, a surgical plan is transferred to a physical model ratherthan the digital jaw model. In this manner, the cavity may be formedafter creation of the physical model using any suitable alignment jigsuch as drill alignment fixture or a dental drilling alignment fixture.A variety of tools for transferring computerized implant plans tophysical models are commercially available and may be adapted to thisapplication, such as the Gonyx device available from Straumann, or avariety of other dental guided surgery systems. Once the cavity ofsuitable depth and orientation has been created, the method 300 may ingeneral proceed as described in the methods above.

As shown in step 302, the method 300 may begin with obtaining a physicalmodel of intraoral structures of a patient. This may be obtained from aphysical impression, or fabricated from a three-dimensional modelobtained using any of the techniques noted above.

As shown in step 304, the method 300 may include creating a surgicalplan for a dental implant in a jaw of the patient, the surgical planincluding an axis for the dental implant.

As shown in step 306, the method 300 may include modifying the physicalmodel to include a cavity formed by a cylinder centered on and parallelto the axis, the cavity having a depth into the physical model along theaxis. This may, for example, include transferring the surgical plan tothe physical model using an alignment jig. A variety of suitablealignment jigs are available in the art. This may include general dentalalignment tools, dental drill alignment indicators, alignment frames,implant positioning hardware, and so forth. In general, any techniquefor transferring an implant plan to a physical model may be usefullyemployed in this context.

As shown in step 310, the method 300 may include placing an insert intothe cavity, the insert having an exposed top surface and an opening inthe exposed top surface. In another aspect, this step may be omitted andthe guide may be fabricated using an insert-less procedure such as thatdescribed below with reference to FIG. 4.

As shown in step 312, the method 300 may include forming a guide from amaterial disposed around the physical model and the insert.

As shown in step 314, the method 300 may include creating a hole in theguide aligned to the opening.

As shown in step 316, the method 300 may include removing the guide fromthe physical model.

FIG. 4 shows a method for fabricating a drill guide. In the embodimentsabove, a sleeve, insert, or other cut resistant perimeter is providedfor formation of a hole in the drill guide. This may, of course beomitted, although additional care might be required in accuratelyforming the hole with a cutting instrument. An insert-free method is setout below, with steps being substantially as set out above except wherenoted.

As shown in step 402, the method 400 may include obtaining a digital jawmodel of intraoral structures of a patient.

As shown in step 404, the method 400 may include creating a surgicalplan for a dental implant in a jaw of the patient, the surgical planincluding an axis for the dental implant, wherein the axis is specifiedrelative to the digital jaw model.

As shown in step 406, the method 400 may include modifying the digitaljaw model to include a cavity having a predetermined orientationrelative to the axis, the cavity extending into the digital jaw model.

As shown in step 408, the method 400 may include fabricating a physicalmodel from the digital jaw model, the physical model including a recesscorresponding to the cavity of the digital jaw model.

As shown in step 412, the method 400 may include forming a guide from amaterial disposed around the physical model.

As shown in step 414, the method 400 may include creating a hole in theguide aligned to the recess. It will be noted that the hole is alignedto the recess in the physical model, and is created without the use ofan insert, sleeve, or other cut-resistant guiding component.

As shown in step 416, the guide may be removed from the physical model.As shown in step 418, the guide may be trimmed and/or finished asappropriate for use in a drilling procedure.

In another aspect there is disclosed herein a guide fabricated using thetechniques described above. This may, for example include a model of oneor more intraoral structures, the model modified to include a retainingfeature to removably retain an object; a sleeve removably held inposition relative to the model by the retaining feature; and a guidevacuum formed to the shape of the one or more intraoral structures andthe sleeve, wherein the sleeve is retained captive in the guide andremovable with the guide from the model.

FIG. 5 shows a modified digital model, or a physical model fabricatedfrom same. The model 500 may be modified as described above to include araised surface 502, e.g., a raised cylinder with a hole on a top surfacethereof. A guide formed around this model will include a hole off of thesurface of the surrounding intraoral structures that is aligned to theimplant plan.

FIG. 6 shows a modified digital model, or a physical model fabricatedfrom same. The model 600 may be modified to include a recess 602 orcavity into which an insert can be placed for creation of a guide asdescribed above.

FIG. 7 shows a modified digital model, or a physical model fabricatedfrom same. The model 700 may be modified to include a post 702 ontowhich a sleeve can be placed for creation of a guide as described above.In some implementations, the sleeve may be captured by the guide (e.g.,via adhesive or other means), so as to form a guide tube to furtherguide a drill.

FIG. 8 illustrates steps to a method for fabricating a guide.

In a first step 802, a digital model of a surgical site may be providedincluding, e.g., dentition, soft tissue, bone, and so forth.

In a second step 804, the digital model may be modified using thevarious techniques described above to provide a modified digital model.For example, a cylindrical opening may be created in dentition and/orjaw around a desired trajectory for a drill. In another aspect, acylindrical post or the like may be created extending upward from thedentition and/or jaw around the desired trajectory. In another aspect, acylindrical post may be created that includes a hole centered in thecylinder. This later configuration creates a hole that is used to createa guiding hole for a drill, along with a drill stop formed from theflat, top surface of the cylinder to guide a drill.

In a third step 806, a physical model may be fabricated based on themodified digital model using, e.g., any suitable fabrication techniquesuch as stereolithography, fused deposition modeling, CNC milling, andso forth.

In a fourth step 808, any suitable insert or combination of inserts maybe added to the model. For example, in the first embodiment noted above(cylindrical hole in jaw), a post or similar insert may be placed intothe hole to form a shape around which a guide may be formed.

In a fifth step 810, a guide may be formed around the physical model andinsert using, e.g., vacuum forming or any other suitable technique forcreated an model formed to the surface of the physical model.

In a sixth step 812, the guide may be removed from the physical modelfor use in a drilling procedure. Any suitable finishing steps may beperformed on the guide, such as trimming, test-fitting, and so forth.

FIG. 9 shows a dental drill with a drill stop. As noted above, a drillstop 902 may be used with a drill bit 904 of predetermined length anddiameter to control the use of a dental drill 906 or the like in adrilling procedure. The drill stop may have a lower section 908 with adiameter fitted to a drill guide, and an upper portion 910 with a flangeor the like that is too large to pass through the drill guide. Thus thedrill stop can provide centering of a drill, while also controlling adepth of drilling by preventing an incursion of the assembled drill,drill bit, and drill stop beyond a predetermined depth into the guide.Furthermore, with parameters such as an implant depth, a series of drillstops may be provided for a series of drill bits with increasingdiameter. If the drill stops have a similar outside diameter, then theycan be used in sequence with a single drill guide in order to createprogressively larger diameter holes centered on a trajectory for animplant plan.

FIG. 10 (in FIGS. 10A-10C) illustrates steps of a technique for using adrill stop. As shown in FIG. 10A, a drill 1001 with a drill bit and adrill stop as described above may be inserted into a drill guide 1002off-axis from the trajectory of an implant plan. The drill guide 1002may, for example, include any of the guides fabricated as describedabove. In some implementations, the path of the drill bit is furtherconstrained by a guide tube (FIG. 13), which keeps the drill biton-axis. As shown in FIG. 10B, the drill bit may then be manuallyaligned to the trajectory and/or the top of a preexisting pilot hole. Asshown in FIG. 10C, drilling may begin. As the drill bit moves into thedrilling site, the drill stop can center the drill to the trajectoryand, at a predetermined depth, stop the drill bit from further incursioninto the drilling site. The drill may then be removed and the drill bitmay be replaced with a larger diameter drill bit and a correspondingdrill stop for drilling a larger hole.

It will be further appreciated that, while a tooth-supported guide isillustrated in FIG. 10, the principles disclosed herein may be suitablyadapted for use with an endentulous guide that rests on the gingivaand/or gum and/or bone and is secured with one or more bone screws.

FIG. 11 shows a multi-layer guide. It may be difficult to manufacture adrill guide which fits the dentition securely and precisely withadequate retention. One challenge is the presence of undercuts in theanatomy of the teeth of varying severity, which are positioned atdiffering angles to each other. The difficulties in achieving a secure,tight fit to dentition may be addressed in part by providing a guide1100 with multiple layers including a first layer 1102 serving as aninterior (e.g., tooth-facing) surface that is pliable and compressible,along with a second layer 1104 that provides an exterior (e.g., facingaway from tooth surfaces) surface that is sufficiently rigid to enforcea planned drill trajectory. In general, the first layer 1102 may includea clearance 1106 away from a hole 1108 for a drill. In general, theclearance 1106 permits the pliable material of the first layer 1102 toavoid contact with a drill that is guided by the hole 1108 in the morerigid second layer 1104, thus preventing the material from the firstlayer 1102 from becoming bound in the drill and entering a surgicalsite.

Accordingly, in one aspect the methods contemplated herein may includeforming a clearance in the first layer 1102 to provide a second holeabout the axis of a drill trajectory, where the second layer has agreater diameter than a corresponding hole 1108 in the second layer1104.

It will be understood that terms such as pliable and rigid are somewhatrelative. As used in this context, the term “rigid” or “substantiallyrigid” is intended to mean sufficiently rigid to maintain a position ofa drill during a drilling procedure as contemplated herein, and adequaterigidity will be readily understood and appreciated by one of ordinaryskill in the art. Similarly, the term “pliable” or “substantiallypliable” is intended to mean sufficiently soft, pliable, and/orcompressible to variably fill a space between a rigid drill guide anddentition by yielding to the dentition and, when compressed, retainingthe relative position of the guide to the dentition with sufficientfidelity for the guide to function adequately. Where precise values forhardness or stiffness are not given, it will be understood that theseterms at least convey a relative difference in such mechanicalproperties. Thus, rigid may be understood to mean more rigid, andpliable may be understood the mean less rigid. Again, suitable physicalproperties will be readily understood by one of ordinary skill in theart, and exemplary values may be ascertained, for example, from theexample materials described below.

FIG. 12 shows a method for fabricating a multi-layer drill guide. In oneaspect, a multi-layer vacuum forming technique may be employed to obtaina drill guide superior gripping and stability when placed for use from acombination of a rigid exterior layer and a pliable interior layer,which multiple layers may be formed, e.g., from a number ofvacuum-forming operations or any other suitable fabrication techniques.It will be noted that terms such as a first layer and a second layer areused below as terms of convenience, and not to require or suggest aparticular order in which the layers are formed unless expressly statedto the contrary. More generally, it should be clear from the variousembodiments described herein that a rigid layer may be formed before apliable layer or a pliable layer may be formed before a rigid layer.

As shown in step 1201, the method may begin with providing a physicalmodel. This may include any of the physical models described above whichmay be based on modified digital models of intraoral structures such asdentition and surrounding tissue for a patient. As described above, themodified digital model may include a feature aligned to an axis for adental implant, and the physical model fabricated from the modifieddigital model may also include the feature (or more precisely, aphysical instantiation of the feature, although the term is usedinterchangeably herein to refer to the digital or physical version ofthe feature). The feature may generally be a cavity, a post, or anyother physical feature described that might represent the intended axis(and corresponding drill trajectory) for the implant.

It will be appreciated that a physical model of one or more intraoralstructures may be fabricated from any corresponding digital jaw modelthat is available for a patient, or the physical model may be obtaineddirectly from a patient using a physical molding or casting technique.It will also be appreciated that the physical model may be useful forcertain fabrication steps such as vacuum forming as described below.However, in other aspects, the physical model may be omitted entirely,and various layers of a multi-layer guide may be fabricated directlyfrom a digital model using any suitable rapid prototyping technologysuch as the various rapid prototyping technologies described herein.

As shown in step 1202, the method may include fabricating a first layerof a pliable material to serve as an underlayer that flexibly conformsto a tooth surface or the like. A model of dentition including a rodindicating the implant position (all as described above) may be used asa model for fabricating the drill guide. Undercuts in the model may beblocked out by filling the undercuts with dental blockout compound(e.g., FILL-IT, a compound made available by AMERICAN DENTAL SUPPLY,INC.), or any other suitable material. A relatively soft, resilientmaterial such as Proform soft ethylene vinyl acetate (EVA) vacuumforming material (0.040″ thick) commercially available from TruTainOrthodontics and Dental Supplies or any similar material may be suitablyused as the first layer, and may be formed onto the model by vacuumforming.

Alternatively, step 1202 may include forming a first layer from a rigidmaterial. The rigid material may be formed into a shell such as any ofthe thin-layered or other shapes and forms described above with aninterior surface corresponding to one or more intraoral structures of apatient's mouth. For example, the rigid material may be a thermoplasticor other material that can be placed into a pliable state through theapplication of heat, light or other stimuli. In this pliable state, therigid material may be disposed onto a physical jaw model and thenreturned to a rigid state (e.g., through cooling). As another example,the rigid material may be a light-curable, heat-curable, air curable orotherwise curable material that can be disposed onto a physical modeland then cured into a rigid form.

In another aspect, the method 1200 may include forming the first layerby fabricating the first layer directly from the rigid material with arapid prototyping system based upon a digital jaw model.

As shown in step 1204, the method 1200 may include trimming the layer.To accomplish this, the first layer of material may be removed from themodel and trimmed to extend to the gingival margin of the teeth. Thematerial may be further trimmed to cover all teeth except the tooth (orteeth) adjacent to the surgical site. More specifically, the materialmay be trimmed to provide a clearance as described above relative to thedrilling trajectory and the drill bit that will be used for drilling.Any suitable setback (shown as a “clearance” in FIG. 11) may be employedprovided that there is sufficient space to avoid interference of thesoft material with a drilling, while covering a sufficient area ofdentition (e.g., other teeth) to provide a stable support for the drillguide. This may, for example be one millimeter, five millimeters, or anyother suitable setback. A larger setback of any suitable size maypreferably be employed to ensure clearance from a drill, provided thefirst layer covers sufficient areas of the surrounding dentition toprovide substantial coverage of tooth support regions.

As shown in step 1206, a second layer may be formed on the first layer.To perform this step, the trimmed first layer may be returned to aphysical model in order to provide rigid support for additionalvacuum-forming. Thus the trimmed soft EVA material may be placed ontothe model and a second layer may be formed on top of the first layer.The second layer may be formed of any suitably rigid plastic or othermaterial(s) such as acrylonitrile butadiene styrene (“ABS”) orpolystyrene. As noted above, a variety of different types of guides maybe formed. Thus the step 1206 of forming the second layer may optionallyinclude adding a guide tube, adding an insert such as a post or guidering, and so forth, prior to forming the second layer. A material suchas Tru-Tain Splint vacuum forming material (0.040″ thick) or any othersuitably rigid material may be vacuum formed onto the model overlayingand laminating the soft EVA underlayer. In some implementations, theguide tube may be captured by the vacuum formed material, thereby beingincluded in the manufactured drill guide. In some implementations, theguide tube need not be captured by the vacuum formed material.

In another aspect where a rigid layer is initially formed with aninterior surface shaped to intraoral structures, step 1206 may includeforming the second layer of a pliable material on the interior surface.This may, for example, include depositing the pliable material onto theinterior of the first layer, such as by painting or otherwise disposingthe pliable material onto the interior surface, or by dipping the rigidlayer into a liquid bath of the pliable material. The pliable materialmay then be cured using any suitable curing or drying technique. It willbe noted that while two layers are described, any number of intermediatelayers may also or instead be employed. For example, where the rigidmaterial is dip-coated in a bath of the pliable material, the resultingdrill guide may include a top and bottom layer of pliable material, witha rigid material encased therebetween. It will also be understood thatsacrificial layers of material may be usefully employed duringprocessing. For example, a physical model may be painted with a spacerto provide room for a coating of pliable material when a rigid materialis formed on the physical model. The space may remain with the physicalmodel when the rigid material is removed, and the resulting impressionin the rigid material will be slightly enlarged, and may accommodate apliable material disposed therein.

In another aspect, the method 1200 may be adapted for use with directthree-dimensional printing of the guide. For example, the modifieddigital model described in step 1201 may be further processed to createa model of a guide conforming to the digital model of the jaw, and thefirst and second layers may be further created as separate digitalmodels for direct fabrication. In step 1202 the first layer may then befabricated directly from a pliable material (either including the hole,or with the hole added in a separate fabrication step prior to addingthe second layer). Then, the trimming step may be omitted, and thesecond layer may be added in step 1206 by directly fabricating thesecond layer (with a second hole that has a diameter less than the holein the first layer) directly on top of the first layer. In this manner,the guide may advantageously be directly fabricated without anyintermediate steps of fabricating a physical jaw model or trimming thehole in the first layer to provide clearance for a drill during use. Avariety of three-dimensional printing techniques may be suitably adaptedto this technique, or similar techniques adapted to the capabilities ofvarious three-dimensional fabrication technologies. All such variationsas would be apparent to one of ordinary skill in the art are intended tofall within the scope of this disclosure.

In another aspect, a composite vacuum-forming material may be used. Forexample, multi-ply vacuum-forming materials are commercially availablewith a polystyrene surface and an EVA surface pre-laminated together.While this may restrict a user's flexibility in terms of types andthicknesses of materials, some of these commercially available laminatesmay be suitable for use in fabricating a multi-layer guide ascontemplated herein.

As shown in step 1208, the completed, composite, multi-layer guide maybe removed from the model.

As shown in step 1210, the guide may be trimmed or otherwise finishedfor use as a dental guide. In one aspect, this may include forming ahole in the first layer and the second layer aligned to the axis of adental implant for which a hole is to be drilled using the guide. Whilethis is illustrated as a final or ending step in a process, it will beunderstood that the hole may be created at any time during fabricationof the guide, and may include two separate and independent steps ofcreating a first hole in the first layer and a second hole in the secondlayer. In another aspect, where a layer is directly fabricated from arapid prototyping system, a source digital model may include anappropriately positioned hole and the layer may be fabricated with thehole already present in the desired location. In another aspect, where aphysical model is adapted to create a corresponding feature, the holemay be created when the first layer is formed onto the physical model.Thus a variety of techniques are generally contemplated for creating ahole for use in a drill guide as contemplated herein, any of which maybe used alone or in combination to create suitable holes in the firstlayer and second layer.

In one aspect, a laminate of soft EVA is thus formed as depicted in FIG.11. The material may be trimmed to the extent of the gingival margin andthe plastic overlaying the guide tube may be trimmed to create a guidehole. The drill guide may then be removed from the model and theperimeter trimmed to a length consistent with appropriate retention onthe plastic model and on the stone model of the patient's dentition. Itshould be noted that the resulting guide has numerous advantages thatmay not be readily apparent. For example, when the rigid material isvacuum formed over the pliable material, the vacuum forming processslightly compresses the pliable material around the shape of the teeth,and when the guide is removed from the physical model, the interiorshape of the pliable material becomes slightly smaller in volume thanthe model as the pliable material elastically expands to its restingstate. As a result, when the guide is placed in a patient's mouth, thepliable material compresses somewhat within the rigid shell to form atighter, more uniform fit to the teeth which, in practice, has beendemonstrated to be significantly more stable than a rigid shell alone,and well suited to use as a drill guide.

In another aspect, the multi-layer model may be fabricated using, e.g.,a rapid prototyping technology such as multi jet or polyjet printing,stereolithography, selective laser sintering, fused deposition modeling,computerized milling, and so forth. In particular, where such afabrication platform has multi-material capabilities, a modelcorresponding to the design described above may be created in athree-dimensional modeling environment, and the model may be fabricatedusing a relatively soft, compressible material as the interior layer anda relatively rigid material as the exterior layer, as described above.Similarly, the interior layer may be fabricated using a rapidprototyping technology based on a digital model of the patient'sdentition, and the rigid exterior layer may be vacuum formed on to theinterior layer. Any such combinations of fabrication techniques forobtaining the model shown in FIG. 11 may be suitably employed. In thesecontexts, the digital model of the teeth may be made slightly smaller inoverall shape and volume so that the pliable layer can compress withinthe rigid layer to provide a more secure bond to tooth structures and,as a result, a more stable drill guide.

In general, the various techniques for fabricating drill guides asdescribed above may employ rapid prototyping techniques in variouscombinations. Thus each physical model (modified or otherwise), eachdrill guide layer, and each drill stop, as well as subcomponents orsubassemblies of the foregoing, may be fabricated using rapidprototyping. By way of non-limiting example, a pole may be fabricatedinto a tooth model, or as a part that fits into a hole in a tooth model,using a three-dimensional printer. In general, the pole serves to aligna guide hole to an intended trajectory. A platform, which may also beprinted, may have a generally annular shape that fits around the poleand establishes a height for a tube that fits over the pole. In thismanner, the tube may be positioned to control drill depth based upon thethickness of the platform.

FIG. 13 shows an exemplary physical model 1302 of a modified digitalmodel that includes a post 1304 to secure a guide tube. FIG. 14 show thephysical model 1402 with a guide tube 1404 (such as a metal tube) placedover the post. As discussed above, a guide may be vacuum formed over themodel and tube so that the tube is captured within the guide to providea metal guiding tube in the resulting drill guide.

It will be appreciated that many of the above systems, devices, methods,processes, and the like may be realized in hardware, software, or anycombination of these suitable for the control, data acquisition, anddata processing described herein. This includes realization in one ormore microprocessors, microcontrollers, embedded microcontrollers,programmable digital signal processors or other programmable devices orprocessing circuitry, along with internal and/or external memory. Thismay also, or instead, include one or more application specificintegrated circuits, programmable gate arrays, programmable array logiccomponents, or any other device or devices that may be configured toprocess electronic signals. It will further be appreciated that arealization of the processes or devices described above may includecomputer-executable code created using a structured programming languagesuch as C, an object oriented programming language such as C++, or anyother high-level or low-level programming language (including assemblylanguages, hardware description languages, and database programminglanguages and technologies) that may be stored, compiled or interpretedto run on one of the above devices, as well as heterogeneouscombinations of processors, processor architectures, or combinations ofdifferent hardware and software. At the same time, processing may bedistributed across devices such as the various systems described above,or all of the functionality may be integrated into a dedicated,standalone device. All such permutations and combinations are intendedto fall within the scope of the present disclosure.

In other embodiments, disclosed herein are computer program productscomprising computer-executable code or computer-usable code that, whenexecuting on one or more computing devices (such as the devices/systemsdescribed above), performs any and/or all of the steps described above.The code may be stored in a computer memory, which may be a memory fromwhich the program executes (such as random access memory associated witha processor), or a storage device such as a disk drive, flash memory orany other optical, electromagnetic, magnetic, infrared or other deviceor combination of devices. In another aspect, any of the processesdescribed above may be embodied in any suitable transmission orpropagation medium carrying the computer-executable code described aboveand/or any inputs or outputs from same.

It will be appreciated that the methods and systems described above areset forth by way of example and not of limitation. Numerous variations,additions, omissions, and other modifications will be apparent to one ofordinary skill in the art. Thus, for example, while dental implantprocedures are clearly contemplated, this disclosure is not limited tooral surgery, but may facilitate any osteotomy, bone surgery, bonereplacement, or other surgical procedure requiring drilling into bone orhard tissue, or more generally any procedure involving alignment of atool to a desired trajectory. In addition, the order or presentation ofmethod steps in the description and drawings above is not intended torequire this order of performing the recited steps unless a particularorder is expressly required or otherwise clear from the context.

It should further be appreciated that unless expressly stated to thecontrary or otherwise clear from the context, each method step recitedherein is intended to include causing that step to be performed by anexternal resource controlled by the disclosed method. Thus for example astep such as fabricating a physical model includes causing the physicalmodel to be fabricated, e.g., by transmitting a digital model to afabrication resource such as any of the prototyping systems describedherein.

While particular embodiments of the present invention have been shownand described, it will be apparent to those skilled in the art thatvarious changes and modifications in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the following claims. The claims that follow are intended toinclude all such variations and modifications that might fall withintheir scope, and should be interpreted in the broadest sense allowableby law.

What is claimed is:
 1. A method for fabricating a drill guidecomprising: obtaining a digital jaw model of one or more intraoralstructures of a patient; creating a surgical plan for a dental implantin a jaw of the patient, the surgical plan including an axis for thedental implant, wherein the axis is specified relative to the digitaljaw model; creating a physical jaw model of the one or more intraoralstructures, the physical jaw model including a feature aligned to theaxis for the dental implant; vacuum forming a first layer of a pliablematerial onto the physical jaw model; and vacuum forming a second layerof a rigid material onto the first layer with a hole aligned to the axisof the dental implant based on the feature in the physical model.
 2. Themethod of claim 1 wherein the rigid material is a thermoplasticmaterial.
 3. The method of claim 1 further comprising forming a secondhole in the first layer aligned to the axis and having a clearance suchthat the second hole in the first layer has a diameter greater than thehole in the second layer.
 4. The method of claim 1 wherein creating thephysical jaw model includes creating the physical jaw model with a rapidprototyping system based upon the digital jaw model.
 5. The method ofclaim 4 wherein the rapid prototyping system includes astereolithography system.
 6. The method of claim 4 wherein the rapidprototyping system includes a computerized milling system.
 7. The methodof claim 4 wherein the rapid prototyping system includes one or more ofa fused deposition modeling system, a selective laser sintering system,and a polyjet printing system.
 8. The method of claim 1 wherein thefirst layer includes ethylene vinyl acetate.
 9. The method of claim 1wherein the second layer includes polystyrene.
 10. The method of claim 1further comprising obtaining the digital jaw model from a scan of thepatient.
 11. The method of claim 10 wherein the digital jaw model isbased upon one or more of a Computed Tomography scan, a Cone BeamComputed Tomography scan, and an x-ray scan, and a Magnetic ResonanceImaging scan.
 12. The method of claim 10 wherein the digital jaw modelis based upon one or more of an optical scan and a laser scan.
 13. Themethod of claim 1 further comprising obtaining the digital jaw modelfrom a physical impression of the jaw of the patient.
 14. The method ofclaim 1 wherein the second layer includes acrylonitrile butadienestyrene.
 15. The method of claim 1 wherein the first layer is providedfor vacuum forming with a thickness of about 0.040 inches.
 16. Themethod of claim 1 wherein the second layer is provided for vacuumforming with a thickness of about 0.040 inches.
 17. The method of claim1 wherein the first layer and the second layer are combined as amulti-ply vacuum-forming material.
 18. The method of claim 17 whereinthe multi-ply vacuum-forming material includes a polystyrene surface andan ethylene vinyl acetate surface pre-laminated together.
 19. The methodof claim 1 wherein the feature of the physical jaw model aligned to theaxis for the dental implant includes a post.
 20. The method of claim 1wherein the feature of the physical jaw model aligned to the axis forthe dental implant includes a cavity.